The present invention provides a technology of electro-optically modulated surface plasmon resonance (SPR) based on phase detection, which can be utilized to sense material characteristics, concentration of biochemical matter, and interaction intensity of biochemical molecules. Moreover, design and manufacture of sensing layers can develop applications of electro-optically modulated SPR, such as sensing drug concentration, sensing affinity of drug and serum albumin, sensing chemical compositions, sensing environmental contamination, and so on. Objections of the invention are increasing sensitivity of SPR, developing system stability, reducing measurement cost, reducing system bulk, and so on.
The SPR is an optical detecting technology, and has advantages of label-free, a real time analysis, specificity, a high sensitivity, an ability of mass parallel detection, and so on. When the incidence light beam inputs an interface between metal and medium, if the component of wave vector of the incidence light beam is equal to the wave vector of the surface plasma wave, the energy transfer from the incidence light beam occurs such that the surface plasma waves is excited on the interface between metal and medium, which is named as SPR. The SPR can evidently change the intensity and the phase of the output optical wave. Property changes of medium on the metal surface can be sensed by detecting changes of the intensity or the phase of the output optical wave.
Currently, methods for modulating the wave vector of the incidence light beam mainly include two kinds: one is modulating the incidence angle of the incidence light beam, and the other is modulating the wavelength of the incidence light beam. The method of modulating the incidence angle of the input light beam utilizes a mechanical device to rotate a prism, and the detection resolution is limited by the resolution and the stability of the mechanical device rotation. Furthermore, the mechanical device has a huge bulk, and is hardly moved and arranged. The method of modulating the wavelength of the incidence light beam utilizes a stable broadband light source and a high resolution spectrometer to detect the spectrum change of the output light beam. The method of modulating the wavelength of the incidence light beam has a high equipment cost and requires a high environmental stability, and therefore, the method is hardly used in outdoors detection.
In TW patent no. I273231, inventors of the present invention provided a method for modulating the wave vector of incidence light beam using the electro-optical effect, which can detect the property changes of medium on metal surface by measuring the slope of a regression straight line of the relation between the intensity of the output light beam and the applied voltage. The method using the electro-optically modulated SPR can reduce interferences from outer noises, system bulk, and system cost. However, because environmental noises heavily interfere the detection of the intensity of optical wave, the detection resolution can not be further improved. Moreover, the phase shift caused by the SPR will acutely changes with the property changes of an under-testing object.
What is needed is a testing method for using electro-optically modulated surface plasmon resonance based on phase detection, which can effectively reduce noises, and improve a detection sensitivity and a detection resolution.